Tank trucks, also known as tanker trucks or simply tankers, are a common type of transport vehicle used for transporting bulk liquid cargo, which may include petroleum products, industrial chemicals, or other products that may pose a risk to health, safety, or the environment. When liquid cargo is transported, the liquid is first loaded into a tank on the tank truck at the place of origin and then unloaded from the tank at the destination of the cargo. To unload liquid cargo, a valve is opened on an offloading line located on the bottom of the tank. A temporary air supply line is typically connected to the top of the tank for supplying air to the tank. Air is supplied to the tank to pressurize the tank in order to facilitate offloading of liquid cargo and to prevent a vacuum on the tank when unloading liquid cargo. Supplied air may be later vented from the tank through the overhead air supply line after disconnecting the temporary air line. Tank trucks typically have piping that connects to the top of the tank and extends down to a low point on the tank truck where an operator can access the piping without climbing onto the top of the tank truck. The piping has a valve and a connection at the low point for hooking up the temporary air line at an offloading site for supplying air to the tank during offloading.
A problem commonly experienced during the transporting of liquid cargo in tank trucks or other transport vehicles is sloshing of the liquid in the tank during transportation due to motion of the vehicle. The sloshing motion of the liquid inside the tank may cause some liquid to backflow into the opening to the air supply piping connected to the top of the tank. Once in the piping, some liquid may then gravity flow to the low point of the piping where operators connect temporary air lines to the piping for supplying air to the tank. Any accumulated liquid at the low point will remain in the piping until drained. This accumulated liquid in the air supply piping may cause operational problems with the system. For instance, in cold weather the liquid may freeze inside the pipe, which may block the flow of air to be supplied to the tank during offloading. This is particularly a problem with aqueous solutions such as caustic. Additionally, operators may be exposed to potentially hazardous liquids when opening the valve in the piping at the low point to connect an air line to the piping, which may pose a health and safety risk to the operator. Some tanks may have a valve located on the air line at the top of the tank, which may prevent sloshing liquid from accumulating in overhead piping. However, this valve is often intentionally left open by operators due to the inconvenience of having to climb onto the top of the tank truck to open the valve before offloading and to close the valve prior to transporting cargo. At times, this valve may also be left open inadvertently, thereby creating a safety risk.
Accordingly, there is a need in the art for a device for restricting liquid backflow through overhead piping during transportation on a transport vehicle due to liquid sloshing. Additionally, there is a need in the art for a device for restricting liquid backflow through overhead piping without requiring the manual closing of a valve on the top of a tank containing the liquid. Additionally, there is a need in the art for a method for restricting liquid backflow through overhead piping during transportation on a transport vehicle due to liquid sloshing.